It has heretofore been proposed to provide a dual-chamber container by extrusion blow molding separate container sections and then securing the sections to each other to form a unitary container assembly. U.S. Pat. No. 5,823,391 is exemplary of this technology. An object of the present invention is to provide a method and apparatus for extruding and blow molding a one-piece integrally formed dual-chamber container in which the container is divided by a wall that is extruded simultaneously with the container sidewalls prior to blow molding, and remains intact during and after blow molding.
A method of making a dual-chamber plastic container in accordance with one aspect of a presently preferred embodiment of the invention includes extruding a tubular plastic body having a peripheral wall and an integrally extruded internal wall dividing the body into separate chambers. The tubular body is captured between mold segments, and the peripheral wall is blow molded within the mold segments by application of air to the chambers simultaneously and at equal pressures. The blow molded container is then removed from the mold segments. In the presently preferred embodiment of the invention, a container finish is first injection molded having a pair of spaced outlet openings, and the hollow tubular body is extruded from the container finish with the central wall extending from between the outlet openings. The finish is injection molded within finish mold tooling by extruding plastic through extrusion tooling that includes an orifice bushing surrounding a manifold tip. The tube is then extruded from the injection molded finish by moving the finish mold tooling relative to the extrusion tooling while continuing to extrude plastic through the extrusion tooling. The mandrel tip of the extrusion tooling includes a central passage through which plastic is extruded to form the central wall. The finish mold tooling includes a core having an air passage with a single inlet and spaced outlets for registry with the chambers. In the most preferred embodiment of the invention, the central wall is planar in the container as molded and sufficiently thin to flex for at least limited self-leveling of fluids between the chambers. In the most preferred embodiment of the invention, the central wall is no more 0.015 inch thick in the container as molded.